Including Graphics

There are two different ways to include graphics, such as a logo, in HTML email messages and this also applies to HTML signature templates. Graphics, or more precisely images, can either be linked or embedded. This section explains the difference between the methods, the advantages and disadvantages to each method, and how to link or embed images.

Linked or Embedded

Linked images are not a part of the message itself, but are normally placed on a public web server, and then referenced in the message body with an <img> tag, as in this example:

<img src="http://www.company.com/images/logo.gif">

The advantages of linked images are a small message size and a low risk of interception by antivirus and anti-spam filters. The disadvantages are that the recipient may not see linked images when viewing the message off-line, and that some email clients may block image download by default (please see additional notes on Microsoft Outlook 2003 below).

Unlike linked images, embedded images are part of the message itself. Embedded images are included as embedded attachments, and then referenced in the message body with an <img> tag, but with an image identifier, known as the "Content Id", instead of a link, as in this example:

<img src="cid:embedded-image">

Note You cannot explicitly create cid references. Microsoft Outlook will do this when configured to embed images, or when an image is stored in a local network location.

The advantages and disadvantages to using embedded images are exactly opposite to using linked images. The message size is (potentially much) larger and the risk of interception by antivirus and anti-spam filters is higher. On the other hand, the recipient will normally see embedded images even when viewing email off-line, and image download blocking issues do not normally apply to embedded images.

How to Include Linked Images

To include linked images, simply insert the image HTTP link in the HTML for the template. Unless the Send pictures from the Internet option in Microsoft Outlook is enabled, the picture will not be embedded in the email. You can control this particular Outlook setting via the signature client settings or global client settings in Email Signature Manager, or via Group Policies (GPO).

How to Include Embedded Images

To include embedded images, you can insert the image HTML link using the file name of the image on a local disk or network share. Microsoft Outlook will automatically recognize that the image is stored locally and embed the image in the email.

Alternatively, when the Send pictures from the Internet option is enabled, pictures will always be embedded. However, using this approach will result in all images in an email to be embedded, i.e. also images that the user has added to the email.

Note Embedded images cannot be used in OWA signatures; OWA signatures must used linked images.

Linked Images in Microsoft Outlook

By default, Microsoft Outlook 2003 and higher block the automatic download of images from the Internet, i.e. the download of linked images. A recipient using Outlook 2003 or higher will see the message and message formatting, but must manually activate the download of pictures. This applies to linked images only; embedded images will be shown automatically.

Outlook 2003 can be configured to automatically download images as follows:
 

Outlook 2007 can be configured to automatically download images as follows:

Outlook 2010 can be configured to automatically download images as follows:

Outlook 2003 and Outlook 2007 can be configured to automatically download images in email from a specific sender or domain as follows:

Outlook 2010 can be configured to automatically download images in email from a specific sender or domain as follows:

Note By default, email from Contacts is automatically trusted so images will be automatically downloaded.